The production of high molecular weight, water-soluble polymers from such monomers as acrylamide has materially increased over the past decade. These polymeric materials find use as flocculants for mining operations to recover ore from slurries, water-treating to remove suspended impurities etc., and also are used extensively in paper-making to aid paper formation and in oil recovery industries. In the production of these polymers by polymerization of their monomers, it has become increasingly important to produce as high a molecular weight polymer as possible because such polymers function more efficiently than lower molecular weight polymers. It has also been evident that the production of such polymers utilizing a higher monomer solids reaction media would enable the production of more useful polymers at a more economical rate.
One major problem in the production of these water-soluble polymers, especially those of acrylamide, has been recovery of the polymer in a dry condition. When producing these polymers, they eventually go through a stage in the processing when they are in the condition of very stiff aqueous gels. Since the solubility of the polymers in water is one of the most important concerns of the ultimate consumer, it has become increasingly important to produce these polymers in such a condition that they dissolve in water as rapidly as possible.
In 1966, Terenzi patented a process, see U.S. Pat. No. 3,255,142, where the polymer gel was extruded into a rapidly flowing stream of liquid in order to break it into particles of gel which would dissolve more easily than larger sections thereof.
In U.S. Pat. Nos. 3,766,120 and 3,714,136 I disclose another process for rendering polymer gels more easily dissolved wherein the gel is cut into fragments of about 1/8 at low temperatures and dried by suspending them in air. Sodium sulfate powdered on the gel particles renders them freeflowing.
None of these procedures, however, has completely solved the problem of easily dissolving particles of high molecular weight water-soluble particles in water. Attempts to grind or crush dried polymer fragments into small particles also has not accomplished this because the particles are mostly non porous. Excessive shearing and grinding also degrade the polymer.
The advent of a process for the production of emulsions of water-soluble polymers by polymerizing the monomers utilizing a water-in-oil emulsifier appeared to be a solution to the dissolution problem. U.S. Pat. Nos. 3,284,393 and 3,826,771 and British Pat. No. 905,779, all of which are hereby incorporated herein by reference, all teach procedures of this type whereby water, a hydrocarbon oil, the water-soluble monomer and an appropriate emulsifier are formed into a water-in-oil emulsion and polymerization of the monomer is then effected in the presence of a suitable catalyst and at 0.degree.-70.degree. C. The attractiveness of the new procedure resided in the fact that the resultant polymer did not have to be recovered therefrom. The polymerization resulted in the formation of a water-in-oil emulsion of the polymer and said emulsion per se could then be used as such for most of the applications mentioned above.
Two problems still existed, however. In the first place, the cost of transporting the emulsion is materially higher than if the polymer per se were being transported. Since the emulsions contain, on the average, only about 25-30% polymer, 70-75% of the material shipped is useless oil and water. Secondly, the emulsions can present a stability problem when exposed to temperatures below their freezing point.
It has therefore now become even more evident that a system for the recovery and isolation of a high molecular weight, rapidly dissolving, water-soluble polymer is needed. This need has been satisfied by my novel invention disclosed hereinbelow.